Lithium ion battery and its positive material

Abstract

The invention discloses a lithium ion battery and a positive material, the positive material possesses a core-shell structure, the material of a core layer is at least one of lithium cobaltate, a ternary material and a lithium manganese material, the material of a shell layer is lithium nickel manganese spinel. The preparation method comprises the following steps: preparing the sol shell layer material, then adding the core layer material in the sol, stirring, drying and calcining to prepare the lithium ion battery positive material with the core-shell structure. In addition, the invention also discloses the lithium ion battery prepared by the positive material with the core-shell structure, the end of charge voltage is 4.3-4.7V(vs. Li), the lithium ion battery has excellent charge and discharge cycling performance and high temperature storage performance under high voltage.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a lithium ion battery and its positive electrode material. Background technique [0002] With the miniaturization and thinning of portable electronic devices such as mobile phones, digital cameras, and notebook computers, the market's requirements for the energy density, cycle life, and safety performance of lithium-ion batteries continue to increase. [0003] Lithium-ion batteries generally include: a positive electrode sheet, a negative electrode sheet, a separator spaced between the positive and negative electrode sheets, and an electrolyte, wherein the positive electrode sheet includes a positive electrode collector and a positive electrode material distributed on the positive electrode collector, and the negative electrode sheet includes The negative electrode collector and the negative electrode material distributed on the negative electrode collector. At present, the ...

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Problems solved by technology

[0004] However, the above cathode materials have their own disadvantages: LiCoO 2 After the charging voltage exceeds 4.2V, especially above 4.5V, the structure is unstable and the safety becomes poor; LiNiO 2 The structure of LiNiCoMnO is unstable and highly oxidizing to the electrolyte; LiNiCoMnO 2 The structure is unstable, and the high-temperature storage performance is not good; the lithium-rich composite material nLi 2 MnO 3 ·(1-n)LiMO 2 (0<n<1) cycle performance is not good

However, during the charge and discharge process, the valence state of Mn changes from +3 to +4, which is prone to Jahn-Teller effect, lattice distortion, volume shrinkage or expansion, and the structure becomes unstable and collapses; at high temperature, especially In a high voltage system, trace amounts of HF in the electrolyte will cause Mn 2+ Dissolution of (4HF+2LiMn 2 o 4 →3γ-MnO 2 +MnF 2 +2LiF+2H 2 O), resulting in the destruction of the spinel structure, greatly accelerating the decay of capacity, so LiMn 2 o 4 Coated cathode materials are not suitable for use at high voltage and high temperature

[0007] Korean patent KR 20060134631, using Li 1+a Ni x co y mn 1-x-y o 2 (0.01≤a1+a Ni x co y mn 1-x-y o 2 The positive electrode material has poor high-temperature storage performance under high voltage, because the Ni in the layered structure 4+ Oxidation is strong, Ni 4+ At high temperature, the electrolyte will be oxidized to produce a large amount of gas, which will cause the battery to swell at high temperature, and the capacity retention rate will be seriously attenuated.

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